Recent rapid development of the biotechnology expands a demand of a flow cytometer and a cell sorter which are more commonly used in the various fields of medicine and biology for automatic analysis and fractionation of multiple cells.
In general, the flow cytometer forms a stream of a sheath flow containing various cell particles aligned in line, which are collected from a living body (blood, etc.) and dyed with a fluorescent labeling reagent, and emits laser beam onto the stream of the cell particles to detect light excited by and/or scattered at the cell particles (i.e., forward-scattered light, and side-scattered light, and multicolor fluorescence varying based on the fluorescent labeling reagent in use) so that each of the cell particles in the stream is analyzed based upon the detected light.
Also the flow cytometer converts the detected light having identification information unique to each of the cell particles into electrical signals, so as to statistically evaluate electrical signals for a mass of the cells collected from the sample, thereby allowing diagnosis of a pathologic condition such as a disease of the living body.
Further the cell sorter uses the electrical signals having identification information of the cell particles to selectively charge droplets containing a particular group of the cells to be sorted, and forms a DC electrical field between a pair of deflectors across a dropping path of the droplet, thereby selectively retrieving or sorting the desired cells.
Especially recent development has proved great efficacy and possibility of the immune cell therapy and/or the stem cell therapy using own stem cells, for which more intensive research is being made. In such research, it is important to establish the technique for sorting or isolating the desired cell particles from the sample liquid. Practically, when the cell sorter is used for sequentially sorting various types of the cell particles within different liquid flows, one of the cell particles in the first liquid flow may possibly be remained somewhere in a system of the cell sorter and mixed with the second liquid flow which is later processed. Thus, it has been reported that according to the conventional art, the sample cell particles might be carried over in the cell sorter and contaminated with the other liquid flow. Also it has been concerned that when the cell particles to be sorted contain HIV virus or hepatitis virus, those harmful cell particles, which are exposed outside the cell sorter and the sorting chamber or suspended in the air, may cause the biological hazard.
One of prior arts disclosed in U.S. Pat. No. 6,880,414 (of which patent family is Japanese Patent Application Publication 2004-69706) teaches a cell sorter which detects an error when the liquid flow containing HIV virus or hepatitis virus is leaked as droplets or aerosol from the sorting block, and uses collection baskets associated with the fin for aspirating droplets and aerosol to a waste or retrieval container.
However, although the cell sorter disclosed in the aforementioned prior art may aspirate some droplets and aerosol from the sorting block, it can hardly recover droplets and aerosol once attached on the sorting chamber. Also according to the prior art, while the droplets and aerosol containing the infectious viruses attached on the sorting chamber may again be evaporated and suspended in the air, the cell sorter may recover them only during activation of the aspirator, but the infectious viruses may be suspended and diffused after deactivation of the aspirator, which brings risks of the infection to workers including operators of the cell sorter. Thus, according to the prior art, the cell sorter cannot be used for the next sorting operation while the aspirator is being activated to aspirate the droplets and aerosol.
Further the above-mentioned cell sorter fails to even address the problem of the cell particles carried over or remained upstream the sorting chamber such as in a sample-liquid flow mechanism, a flow cell, and a strobe block, which may be contaminated in another liquid flow.
Therefore, the present invention is made for solving such a problem, and one aspect of the present invention is to provide a flow cytometer and a cell sorter eliminating or substantially reducing the possibility that the cell particles within the liquid flow processed in the previous sorting step are remained in components of the system such as a sample-liquid flow mechanism, a flow-defining block, a strobe block, and a sorting chamber, and contaminated in another liquid flow processed in the successive sorting step.